Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy characterized by poor prognosis, therapeutic resistance, and frequent recurrence. Current therapeutic options for PDAC include surgery, radiotherapy, immunological and targeted approaches. However, all these therapies provide only a slight improvement in patient survival. Consequently, the discovery of novel specific targets is becoming a priority to develop more effective treatments for PDAC. Mucin 1 (MUC1), a transmembrane glycoprotein, is aberrantly glycosylated and frequently overexpressed in pancreatic cancer. Recent studies highlighted the role of this oncoprotein in pancreatic carcinogenesis and its involvement in the acquisition of typical aggressive features of PDAC, like local invasion, metastases, and drug resistance. This review explores the mechanisms by which MUC1 contributes to cancer onset and progression, with a focus on its potential role as a biomarker and novel therapeutic target for pancreatic adenocarcinoma treatment.

Chemotherapy and immunotherapy have markedly improved the management of several malignancies. However, not all cancer patients respond primarily to such therapies, and others can become resistant during treatment. Thus, identification of the factors/mechanisms underlying cancer resistance to such treatments could help develop novel effective therapeutic compounds. Tumor-associated macrophages (TAMs), myeloid-derived suppressor cells (MDSCs), and regulatory T cells (Tregs) are major components of the suppressive tumor microenvironment and are critical drivers of immunosuppression, creating a tumor-promoting and drug-resistant niche. In this regard, therapeutic strategies to tackle immunosuppressive cells are an interesting option to increase anti-tumor immune responses and overcome the occurrence of drug resistance. Accumulating evidence indicates that interleukin-34 (IL-34), a cytokine produced by cancer cells, and/or TAMs act as a linker between induction of a tumor-associated immunosuppressive microenvironment and drug resistance. In this article, we review the current data supporting the role of IL-34 in the differentiation/function of immune suppressive cells and, hence, in the mechanisms leading to therapeutic resistance in various cancers.

Colorectal cancer (CRC) is one of the most frequent neoplasms and a major cause of cancer death worldwide. Despite recent advances in treatment approaches, the prognosis of advanced CRC remains poor, thus indicating the necessity of more effective treatments for CRC patients. CRC cells produce high levels of hepcidin, a peptide hormone that binds to the membrane-bound ferroportin and promotes its internalization and degradation, thus sequestering iron into the cancer cells with the downstream effect of enhancing tumor growth. Additionally, CRC cell-expressed hepcidin prolongs cell survival and, by targeting both CD8+ T cells and myeloid cells, restrains the induction of an efficient immune response against tumor antigens. The greatest expression of hepcidin is found in patients with metastatic CRC, and CRC patients with high hepcidin content have a worse survival rate than those with low hepcidin content. In the present article, we review the data supporting the prominent role of hepcidin in colon tumorigenesis and discuss how hepcidin inhibitors can help treat CRC patients in the metastatic setting with particular regard to the impact of hepcidin modulation on immunotherapeutic outcomes.

The reorganization of the cell cytoskeleton and changes in the content of cell adhesion molecules are crucial during the metastatic spread of tumor cells. Colorectal cancer (CRC) cells express high SMAD7, a protein involved in the control of CRC cell growth. In the present study, we evaluated whether SMAD7 regulates the cytoskeleton reorganization and dynamics in CRC. Knockdown of SMAD7 with a specific antisense oligonucleotide (AS) in HCT116 and DLD1, two human CRC cell lines, reduced the migration rate and the content of F-ACTIN filaments. A gene array, real-time PCR, and Western blotting of SMAD7 AS-treated cells showed a marked down-regulation of the X-linked inhibitor of apoptosis protein (XIAP), a member of the inhibitor of apoptosis family, which has been implicated in cancer cell migration. IL-6 and IL-22, two cytokines that activate STAT3, enhanced XIAP in cancer cells, and such induction was attenuated in SMAD7-deficient cells. Finally, in human CRC, SMAD7 mRNA correlated with XIAP expression. Our data show that SMAD7 positively regulates XIAP expression and migration of CRC cells, and suggest a mechanism by which SMAD7 controls the architecture components of the CRC cell cytoskeleton.

Colorectal cancer (CRC) progression is shaped by dynamic interactions between tumor-intrinsic metabolic adaptations and immune remodeling within the tumor microenvironment. In CRC, the expression of SMAD7, a classical inhibitor of TGF-β1 signaling, is increased and has been associated with tumor-associated inflammatory responses and malignant progression. In this study, we investigated the potential role of SMAD7 in regulating glycolytic metabolism and macrophage phenotype in CRC. Knockdown of SMAD7 in CRC cell lines resulted in reduced glycolytic activity, as demonstrated by decreased extracellular acidification rate, basal glycolysis, and glycolytic capacity. These metabolic changes were associated with reduced expression of the basal and IL-6- and IL-22-induced glycolytic enzyme hexokinase 2 (HK2), while glucose uptake was increased. Similar reductions in HK2 expression were observed in patient-derived CRC organoids following SMAD7 inhibition, supporting the relevance of this pathway in human tumor-derived models. Functionally, SMAD7 knockdown reduced lactate production by CRC cells and diminished the ability of tumor cell-derived conditioned medium to induce the expression of macrophage-associated immunoregulatory markers, including CD163, CD206, and ARG1. The addition of exogenous lactate restored these effects, indicating that tumor-derived lactate contributes to SMAD7-dependent control of the expression of macrophage-associated immunoregulatory markers. Analysis of human CRC transcriptomic datasets revealed positive associations between SMAD7 expression and macrophage-related signatures, including profiles associated with immunoregulatory tumor-associated macrophages. Together, these findings support a potential role for SMAD7 in controlling tumor metabolism and macrophage-associated immunoregulatory markers in CRC.